# Warning: Ambiguous first argument; make sure

**URL:** <https://www.ruby-forum.com/t/warning-ambiguous-first-argument-make-sure/152638>\
**Category:** Rails\
**Created:** [November 5, 2008, 10:15pm UTC](https://www.ruby-forum.com/t/warning-ambiguous-first-argument-make-sure/152638 "2008-11-05T22:15:38Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![cojones](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9f8e36/32.png) [@cojones](https://www.ruby-forum.com/u/cojones)\
**Post date:** [November 5, 2008, 10:15pm UTC](https://www.ruby-forum.com/t/warning-ambiguous-first-argument-make-sure/152638/1 "2008-11-05T22:15:38Z")

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Hello,

I’m getting this warning:

Warning: Ambiguous first argument; make sure.

in my unit test:

assert\_match /^[a-zA-Z0-9]+$/, user.username

Does anyone know why or how to change it so it disappears?

Thanks

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**Author:** ![cojones](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9f8e36/32.png) [@cojones](https://www.ruby-forum.com/u/cojones)\
**Post date:** [November 6, 2008, 4:42pm UTC](https://www.ruby-forum.com/t/warning-ambiguous-first-argument-make-sure/152638/2 "2008-11-06T16:42:26Z")

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Quoting Heinz S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):

> Does anyone know why or how to change it so it disappears?

IIRC, parentheses fix the warning. I.e.,

assert\_match(/^[a-zA-Z0-9]+$/, user.username)

Why it is ambiguous I will leave to someone better in Ruby than I.

HTH,  
Jeffrey

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<div class="post-metadata">

**Author:** ![cojones](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/9f8e36/32.png) [@cojones](https://www.ruby-forum.com/u/cojones)\
**Post date:** [December 2, 2008, 2:54pm UTC](https://www.ruby-forum.com/t/warning-ambiguous-first-argument-make-sure/152638/3 "2008-12-02T14:54:49Z")

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Thanks!